ch4-pv2-virtual-process-memory

1
Ch4 Virtual Process Memory
Bob.Fu
勿上傳公司網站

2
● Page Table(ARM32)
● Task & Page Table
● Process Mapping
● Page Fault(ARM32)

5
Page Table
0x0
virtual address
page table
level 1
physical address
1m
4096
level 1
indexVA
1m

6
Page Table
0x0
virtual address
page table
level 1
page table
level 2
physical address
4k
4k
1m
4096
256
VA
level 1
index
level 2
index
1m

7
Task & Page Table
1. 一個 page table 代表一個 virtual space

8
Task & Page Table
app
mm
1. 一個 page table 代表一個 virtual space
2. 一個 task 對應一個 page table( 透過 mm)

9
Task & Page Table
kthread kthread app2
app3
thread2
app
app3
thread1
TTBR0
mmmm mm mm

10
Task & Page Table
vma
vma
user space 建 mapping --> 建 vma
kernel space 建 mapping --> 填 page table
注意 : 建 vma 不代表填 page table( 等 fault 填 )
vma
app1
mm

12
Process Mapping
vma
vma
vma
task
mm
parent

13
Process Mapping
vma
vma
vma
vma
vma
vma
task
mm
task
mm
fork
parent child

14
Process Mapping
vma
vma
vma
task
mm
vma
vma
vma
mm
task
vma
mm
fork execve
parent child

15
Process Mapping
vma
vma
vma
parent task
virtual physical

16
Process Mapping
vma
vma
vma
vma
vma
vma
parent task
virtual physical
child task
virtual
fork

17
Process Mapping
vma
vma
vma
vma
vma
vma
parent task
virtual physical
child task
virtual
if write?

18
Process Mapping
vma
vma
vma
parent task
virtual physical
child task
virtual
vma
execve

19
Process Mapping
physical
child task
virtual
vma [stack]

20
Process Mapping
physical
child task
virtual vma app-text
vma app-data
vma [heap]
vma [sigpage]
vma ld-text
vma ld-data
vma [stack]
不會先 fault
但 fault 了會 readahead

21
Process Mapping
physical
child task
virtual vma app-text
vma app-data
vma [heap]
vma [sigpage]
vma ld-text
vma ld-data
vma [stack]
vma libc-text
vma libc-data
vma libgcc-text
vma libgcc-data
vma libgcc-text
vma libgcc-data

22
Process Mapping
physical
child task
virtual vma app-text [file mapping]
vma app-data
vma [heap] [anonymous mapping]
vma [sigpage]
vma ld-text
vma ld-data
vma [stack]
vma libc-text
vma libc-data
vma libgcc-text
vma libgcc-data
vma libgcc-text
vma libgcc-data
argument
environment

24
Page Fault
dabt@svc
dabt@usr
pabt@svc
pabt@usr
0
5
7
31
0
5
15
7
31
15
do_page_fault
1. copy on write
2. file mapping
3. anonymous mapping
4. swap(ch18)
5. real bug

25
Page Fault: Copy on Write
parent task
virtual physical
child task
virtual
if write?
1. 配置 pfn
(highmem 佳 )

26
parent task
virtual physical
child task
virtual
if write?
1. 配置 pfn
(highmem 佳 )
2. 複製 data

27
parent task
virtual physical
child task
virtual
if write?
1. 配置 pfn
(highmem 佳 )
2. 複製 data
3. 改 page table

28
Page Fault: File Mapping
physical
child task
virtual vma app-text [file mapping]
vma app-data
vma [heap]
disk
fault@file_mapping
1. 配置 pfn
(highmem 佳 )

29
vma app-text [file mapping]
vma app-data
vma [heap]
disk
read in
fault@file_mapping
1. 配置 pfn
(highmem 佳 )
2. 讀入 data
physical
child task
virtual

30
vma app-data
vma [heap]
disk
read in
fault@file_mapping
1. 配置 pfn
(highmem 佳 )
2. 讀入 data
3. 填 page table
physical
child task
virtual

31
Page Fault: Anon Mapping
vma app-data
disk
read in
fault@file_mapping
1. 配置 pfn
(highmem 佳 )
2. 讀入 data
3. 填 page table
fault@anon_mapping
1. 配置 pfn
(highmem 佳 )
physical
child task
virtual

32
vma app-data
disk
read in
fault@file_mapping
1. 配置 pfn
(highmem 佳 )
2. 讀入 data
3. 填 page table
fault@anon_mapping
1. 配置 pfn
(highmem 佳 )
2. memset 0
physical
child task
virtual

33
vma app-data
disk
read in
fault@file_mapping
1. 配置 pfn
(highmem 佳 )
2. 讀入 data
3. 填 page table
fault@anon_mapping
1. 配置 pfn
(highmem 佳 )
2. memset 0
3. 填 page table
physical
child task
virtual

ch4-pv2-virtual-process-memory

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